In a hydronic heating system, what is the heat transfer medium?

In a hydronic heating system, what is the heat transfer medium?

• A. Air
• B. Steam
• C. Water
• D. Oil

Answer: (C)

In a hydronic heating system, a liquid is circulated to move heat from the boiler to the emitters. The medium needs to store and transfer a lot of energy efficiently within the piping, and water is ideal for this role. It has a high heat capacity, so it can carry more heat per unit mass, and it flows readily through pipes to radiators, baseboards, or radiant floors. Water also remains liquid over the typical operating temperature range and is economical and safe for circulating through the system. Steam, air, and oil serve different purposes in other heating contexts—steam is used in steam systems, air is used in air-based heating, and oil is usually the fuel for the boiler rather than the circulating heat-transfer medium. So the heat transfer medium in a hydronic system is water.

In a hydronic heating system, a liquid is circulated to move heat from the boiler to the emitters. The medium needs to store and transfer a lot of energy efficiently within the piping, and water is ideal for this role. It has a high heat capacity, so it can carry more heat per unit mass, and it flows readily through pipes to radiators, baseboards, or radiant floors. Water also remains liquid over the typical operating temperature range and is economical and safe for circulating through the system. Steam, air, and oil serve different purposes in other heating contexts—steam is used in steam systems, air is used in air-based heating, and oil is usually the fuel for the boiler rather than the circulating heat-transfer medium. So the heat transfer medium in a hydronic system is water.